Testosterone is a word that often brings to mind images
of big men, big trucks and gladiator-style football. After all, testosterone is considered to be the principal male hormone,
playing an important role in the development and maintenance of typical masculine characteristics, such as facial hair, muscle
mass and a deeper voice. So why would women want testosterone? The fact is, women produce it too, and it has more positive
influences than you might think.

Carpenter, M.D., is a consultant in endocrinology and health informatics
research at Mayo Clinic, Rochester, Minn. He has practiced in endocrinology, with a special interest in hormone replacement,
for 25 years. Here he addresses questions about the role of testosterone in women.

Testosterone is usually thought of as a male hormone, but women have
it, too. How much testosterone do women produce?

Testosterone production is substantially lower in women than it is in
men. After puberty, a woman begins to produce a constant, adult level of testosterone. The production is split about 50:50
between the ovaries and the adrenal glands. In men, the testes produce testosterone. Women produce just a fraction of the
amount of testosterone each day that men do.

What does testosterone do for women?

Studies show that it helps maintain muscle and bone and contributes to
sex drive, or libido. There are also quality-of-life issues. If you give testosterone replacement to testosterone-deficient
women, they often say they feel better, but they're not specific as to how.

One of the tough things about research in this area is what has been
measured and what hasn't. Testosterone levels, muscle mass and bone strength have been measured. When testosterone levels
in the blood increase, bone density generally improves. Although a few researchers have attempted to measure changes in sex
drive and overall quality of life, these important effects are much more difficult to assess. A study in the New England
Journal of Medicine evaluated sexuality and quality of life in women with low blood levels of testosterone. After raising
their blood levels of testosterone using a medicated skin patch, health and sexuality seemed to improve.

Which women should have their testosterone levels checked?

It's a complicated answer. After menopause, testosterone production drops,
but not as sharply as estrogen does. For women who've had their ovaries removed, testosterone production drops by roughly
one-half, sometimes resulting in less-than-normal testosterone blood levels.

Generally, the women who have too little testosterone are those who may
go to their doctor with concerns like, "Ever since I had my ovaries removed, I don't feel like the same person. I'm not as
strong, I don't have as much energy and I don't have the same sex drive." Should we measure testosterone in all women who've
had their ovaries removed? I don't know. If a woman says her sex life has diminished since her hysterectomy, her doctor may
check her testosterone level. If it's low, she can consider testosterone replacement.

Another group at risk of low testosterone is women who have lost pituitary
gland function because of a medical condition or past surgery. The pituitary sends hormone messages to the adrenal glands
and ovaries. Without the pituitary signal, hormones aren't manufactured. These women require estrogen and cortisone replacement,
and they're also testosterone deficient. This isn't a common problem, however.

Why aren't more women being given testosterone replacement?

It's true that very few women are getting testosterone replacement. As
I've indicated, good studies about deficiency are sparse. Because of that, many doctors aren't yet convinced of the benefits.
In testosterone replacement studies done 15 or 20 years ago, the doses were often too high. As a result, there were side effects,
such as body hair growth and acne.

Another major problem is that we don't have good product choices to give
women because the drug companies don't manufacture many products for testosterone replacement in women. In the New England
Journal of Medicine study mentioned before, researchers tested a skin patch designed for women. Unfortunately, this patch
isn't yet available but may well be in the future. Testosterone patches are available for men, and there is a testosterone
gel they can apply to their skin. But because women would need a much smaller dose, they cannot use the patches or gels designed
for men.

Right now there's really not a good way to replace testosterone in women.
We can use injections, but most women don't want to come in for a shot every 2 or 3 weeks, and the blood levels are hard to
regulate. After an injection, testosterone levels may go up too high, then decline, like a roller coaster. There's no pure
testosterone in pill form either. Synthetic pills are available but tend to be unevenly absorbed into the body and may pose
some risk to the liver. Testosterone delivered through the skin with a patch is absorbed quite evenly and seems more natural,
with less potential for serious side effects. Using patches doesn't appear to be risky as long as the dose is regulated.

How important is it for women with low testosterone to have it replaced?

It isn't an imminent health danger per se. However, think about the older
woman with osteoporosis who has fallen and fractured her hip. If her testosterone is low, would replacement have helped prevent
her hip fracture? It's possible. Testosterone has the potential to strengthen her bones. Additionally, she might have been
able to prevent the fall if her muscle mass had been better.

If a postmenopausal woman is on hormone replacement therapy (HRT),
does that affect her need for testosterone?

Yes. Estrogen therapy — with or without progesterone — can
further suppress residual testosterone production by the ovaries. That's because hormone signals from the pituitary gland
drive ovarian hormone production. Taking estrogen partially reduces the pituitary hormone signal to the ovaries and potentially
reduces testosterone production. The pituitary senses there's enough estrogen, so it doesn't send the signal for more estrogen
and testosterone.

What are the side effects of testosterone replacement?

When given in appropriate doses, there are no negative side effects.
Today we can measure blood levels, so it's easier to monitor the dose. Excessive testosterone can cause acne, body hair growth
and scalp hair loss in women. Excessive testosterone supplementation, such as you'll find with anabolic steroids used by athletes,
also tends to drop high-density lipoprotein (HDL) cholesterol levels. That's the "good" cholesterol. Lower HDL levels increase
the risk of heart disease.

What about other androgens, such as dehydroepiandrosterone (DHEA)?

DHEA is a weak androgen or male hormone. Although it's true that DHEA
levels decline with age, very few well-designed research studies show benefit from replacement. Another New England Journal
of Medicine study says DHEA treatment improves sexual function in women who have underactive adrenal glands, but not many
people are using the supplement for that reason. In addition, many people are taking DHEA in very large quantities. Again,
excessive amounts of synthetic androgens drive down HDL cholesterol levels, which is considered a cardiovascular risk. People
who are ill often have lower-than-normal DHEA or testosterone levels. This appears to be a normal physiologic response to
illness and not the cause of the illness.